1. Field of the Invention
The present invention pertains to the field of document scanner computer peripherals. In particular, the present invention is drawn to precision deep input guide clips that guide the document over the image sensor at an optimal angle and at an optimal pressure, and to document scanners using the same.
2. Description of the Related Art
Document scanners are computer peripherals that allow users to scan documents into their computers for later storage, retrieval and/or manipulation. Although document scanners are extremely useful peripherals, they have not yet attained the ubiquity of other common peripherals, such as CD-ROM or DVD drives, printers, modems or multimedia sound cards, for example. This state of affairs persists despite the fact that prices for document scanners for personal computers are low and continue to decline rapidly. It does not appear, therefore, that price constitutes a significant barrier to entry for consumers seeking to upgrade the functionality of their personal computers and for manufacturers seeking to integrate scanners into their own products. Instead, it is believed that document scanners have not, to date, realized their anticipated success due to a combination of shortcomings including lack of integration, poor reliability, difficulty of use and slow speed.
Several types of scanners exist, each type being specifically designed for a particular purpose: monochrome, color, sheet-fed, flatbed, handheld, photo-print, photo-slide, SCSI host interface, printer port host interface, IEEE1284 parallel port host interface, serial port host interface, USB host interface, IEEE1394 FireWire host interface, etc. Development costs and time to market are therefore significant. Only scanner manufacturers that are fully committed to document scanner products can afford to be involved in document scanner developments. Manufacturers that wish to incorporate document scanner functions into other types of equipment (multifunction terminals, consumer appliances, gaming devices for example) in order to differentiate their products from those of the competition have experienced difficulties in meeting their goal.
FIG. 1 shows a typical arrangement for a sheet-fed document scanner. In FIG. 1, a document 1 is displaced by a rotating roller paper feeding mechanism 3 driven by a motor 4 over a fixed image sensor 2 that senses reflected light from the document 1. Alternatively, the paper feeding mechanism may be a belt, a plurality of rollers or a combination of one or more rollers and belts. Illumination is provided from the image sensor 2. The image sensor 2, together with its associated electronics (not shown), records a line of information at a time. When the document 1 is driven by the motor 4 and the roller 3, the image sensor 2 records the entire document area swept. The scanner control electronics and the communication link with the host computer are not shown, for clarity.
FIG. 2 shows a typical arrangement for a duplex document scanner. In FIG. 2, a document 1 is displaced by two rotating rollers 3 and 6 driven by a motor 4 over two fixed image sensors 2 and 5 that sense reflected light from each side of the document. Alternatively, the paper feeding mechanism may be a plurality of belts (one shown at reference numeral 7 in FIG. 2), or a plurality of rollers and belts. Illumination is provided from each image sensor 2, 5. The image sensors 2, 5, together with their associated electronics (not shown), record a line of information for each side of the document 1. When the document 1 is driven by the motor 4 and the rollers 3, 6, the image sensors 2, 5, together with their associated electronics, record the entire area swept of the document 1 on both sides thereof. The scanner control electronics and the communication link with the host computer are not shown in FIG. 2.
The image sensors used in sheet-fed and duplex scanners, for example, may be charge-coupled devices (CCD), monochrome or color sensors having a width of approximately 40 to 60 mm fitted with a suitable optical apparatus to reduce the image of the document and an illumination source or monochrome or color contact image sensors (CIS). These image sensors are usually available in B6, A4, A3 sizes or approximately 100 mm to 300 mm. The image sensors produce an analog signal that is commonly called a video signal. Illumination for sheet-fed and other types of scanners (e.g., flatbed scanners, slides scanners) and duplex scanners may be produced using light emitting diodes (LED), cold cathode fluorescent light (CCFL) tubes, electro-luminescent screens or filament lamps, for example. Color dropout (the elimination of a color) may be produced by using color filters that block a selected wavelength or by selecting light sources that generate the selected wavelength.
In both of the scanners shown in FIGS. 1 and 2, however, the document 1 is dragged across the surface of the glass covering the image sensors 2, 5. The document 1, however, may be soiled, and have abrasive particles clinging thereto. The document 1 moreover, even though apparently unsoiled, may itself contain abrasive impurities therein. In addition, the ink used on the document 1 may not be fully dry and may leave an oily residue on the image sensor transparent (typically glass) surface. These abrasive particles, impurities and residues may, with repeated usage, scratch and obscure the surface of the glass covering the image sensors 2, 5, thereby degrading the quality of the resulting scanned image. This scratching may be further exacerbated by the roller 3, 6 pressing the document 1 against the glass of the image sensors 2, 5 with too great a pressure. The quality of the scanned images may also suffer from the effects of parasitic ambient light impinging upon the image sensors 2, 5. Such ambient light may reach the sensors 2, 5 as the sensors 2, 5 are not protected therefrom, particularly when the leading edge of the document 1 is dragged across the sensors 2, 5.
What are needed, therefore, are improved scanners that do not suffer from the forementioned disadvantages. Specifically, what are needed are document scanners with improved resistance to such soiling, scratching or obscuring of the image sensor glass. What are also needed are document scanners and associated document feeding mechanism that eliminate or reduce the amount of parasitic ambient light that is allowed to reach the scanner sensors.
An object of the present invention, therefore, is to provide document scanners that are resistant to such soiling, scratching or obscuring of the sensor glass or other corresponding transparent surface. It is another object of the present invention to provide a document scanner having an improved document feeding mechanism that introduces the document into the scanner at an optimal angle and at an optimal pressure to eliminate or reduce the glass scratching problems often associated with conventional document scanners, even when subjected to heavy usage patterns. Such a document scanner should also protect the image sensors from parasitic ambient light, thereby resulting in an improved scanned image quality.
In accordance with the above-described objects and those that will be mentioned and will become apparent below, a document scanner, according to an embodiment of the present invention, comprises:
an image sensor, the image sensor including a transparent surface over an optical focus line;
a feed roller motor;
a rotatable feed roller coupled to the feed roller motor, the feed roller being adapted to contact said transparent surface along a contact line that is offset from said optical focus line; and
a generally U-shaped deep input guide clip, the deep input guide clip including a plurality of retaining bends to clip onto the image sensor and including a document facing surface defining an opening aligned with the transparent surface, the retaining bends precisely locating the optical focus line relative to the contact line.
According to further embodiments, the deep input guide clip may be shaped from a single sheet of material, such as plastic or sheet metal. The generally U-shaped deep input guide clip may include a pair of facing arms extending from a closed portion of the U-shape, the pair of facing arms being resiliently biased toward one another. The deep input guide clip may include a plurality of spaced cutouts adapted to trap dust as a document is introduced into the scanner. A plurality of document proximity sensors may also be included to detect the leading edge, width and trailing edge of the document introduced into the scanner, the proximity sensors being secured within the deep input guide clip. The proximity sensors may be secured within the deep input guide clip by selected ones of the retaining bends and by proximity sensor folds integral to the deep input guide clip, an active portion of each of the plurality of document proximity sensors being aligned with a corresponding one of the plurality of spaced cutouts. An edge of the document facing surface may be disposed so as to scrape the document as it is introduced into the scanner. The optical focus line may be disposed between the edge of the document facing surface and the contact line, the pressure on the document during a scanning operation being greater at the contact line than at the optical focus line. A primary input guide may be provided, including a generally planar first surface angled relative to the document facing surface, and a generally arcuate second surface facing the feed roller in close proximity therewith and having a curvature generally matching that of the feed roller. In this manner, the primary input guide constrains a path of the document between the first surface and the document facing surface and prevents the feed roller from catching the document until the document is deeply engaged within the scanner. The image sensor may include a contact image sensor and the plurality of document proximity sensors may include infrared sensors.
The present invention may also be viewed as a one-piece deep input guide clip to secure an image sensor of a document scanner, the guide clip including a closed portion from which a pair of facing arms extend, the facing arms being resiliently biased toward one another and including a plurality of retaining bends to clip onto and precisely locate at least an image sensor between the pair of facing arms, the guide clip further including a document facing surface, the document facing surface defining a plurality of cutouts adapted to trap dust and to provide openings for document proximity sensors.
According to still further embodiments, the document facing surface further defines a transparent surface opening to accommodate a transparent surface of the image sensor. The deep input guide clip may be formed of either plastic or sheet metal. The closed portion may define at least one proximity sensor fold extending between the facing arms to secure, in combination with at least one of the plurality of retaining bends, a document proximity sensor assembly. Each of the plurality of retaining bends may be formed, for example, by cutting out three sides of a rectangular window in one arm of the pair of facing arms and pushing a remaining portion of the window toward the other arm of the pair of facing arms. A first retaining bend of the plurality of retaining bends may be located at the free extremity of one of the facing arms and may form a continuous rail along a width thereof, the rail being configured to clip onto the image sensor. One or more second retaining bends of the plurality of retaining bends may be shaped as. a slender extension bent at a free extremity thereof to clip onto the image sensor.
A document scanner, according to another embodiment of the present invention, comprises:
image sensing means, the image sensing means including a transparent surface over an optical focus line;
feed roller motor means;
a rotatable roller means coupled to the feed roller motor means, the feed roller means being adapted to contact said transparent surface along a contact line that is offset from said optical focus line; and
deep input guide clip means, the deep input guide clip means including means for precisely locating the optical focus line relative to the contact line such that a pressure on a document during a scanning operation is greater at the contact line than at the optical focus line.
According to further embodiments, the pressure on the document at the optical focus line may be substantially null. The deep input guide clip means may include a plurality of integral retaining bend means to clip onto the image sensor means, and may include a document facing surface defining an opening aligned with the transparent surface, the integral retaining bend means precisely locating the optical focus line relative to the contact line. The deep input guide clip means may be shaped from a single sheet of material, such as plastic or sheet metal. The deep input guide clip means may be generally U-shaped and may include a pair of facing arm means extending from a closed portion of the U-shape, the pair of facing arm means being resiliently biased toward one another. The deep input guide clip means may include a plurality of dust trap means to trap dust as a document is introduced into the scanner. A plurality of document proximity sensor means may also be provided to detect a leading edge, width and trailing edge of a document introduced into the scanner, the proximity sensor means being secured within the deep input guide clip means. The proximity sensor means may be secured within the deep input guide clip means by selected ones of a plurality of retaining bend means integral to the guide clip means and by at least one proximity sensor fold means integral to the deep input guide clip means, an active portion of each of the plurality of document proximity sensor means being aligned with a corresponding one of the plurality of dust trap means. Scrapping means may also be provided to scrape the document as it is introduced into the scanner. A primary input guide means may include a generally planar first surface angled relative to a surface of the deep input guide clip means adapted to face the document; and a generally arcuate second surface facing the feed roller means in close proximity therewith and having a curvature generally matching that of the feed roller means. In this manner, the primary input guide means constrains a path of the document between the first surface and the document facing surface and prevents the feed roller means from catching the document until the document is deeply engaged within the scanner. The image sensor means may include a contact image sensor and the plurality of document proximity sensor means may include infrared sensors.
The foregoing and other features of the invention are described in detail below and set forth in the appended claims.